短螺旋体新种猪鸭短螺旋体，一种从猪和野鸭中分离出的肠道致病性肠道螺旋体：基因组和表型特征
Brachyspira suanatina sp. nov., an enteropathogenic intestinal spirochaete isolated from pigs and mallards: genomic and phenotypic characteristics.
作者信息
Mushtaq Mamoona, Zubair Saima, Råsbäck Therese, Bongcam-Rudloff Erik, Jansson Désirée S
机构信息
Department of Animal Breeding and Genetics, Global Bioinformatics Centre, Swedish University of Agricultural Sciences (SLU), SE750 07, Uppsala, Sweden.
Department of Bacteriology, National Veterinary Institute (SVA), SE751 89, Uppsala, Sweden.
出版信息
BMC Microbiol. 2015 Oct 12;15:208. doi: 10.1186/s12866-015-0537-y.
BACKGROUND
The genus Brachyspira currently encompasses seven valid species that colonize the intestines of mammals and birds. In a previous study a group of strongly haemolytic isolates from pigs and mallards was provisionally described as a new species within genus Brachyspira, "B. suanatina", and enteropathogenic properties were demonstrated in a porcine challenge model.
METHODS
In the current study characterization of B. suanatina was performed on the basis of cell morphology, growth characteristics, enzyme profiles, DNA-DNA hybridization (DDH) and whole genome comparisons. The draft genome sequence of B. suanatina strain AN4859/03 was determined and compared with the available genomes of all valid species of Brachyspira.
RESULTS
According to morphological traits, growth characteristics and enzymatic profiles, B. suanatina was similar to the type strain of B. hyodysenteriae, but using the recommended threshold value of 70% similarity by DDH it did not belong to any of the recognized Brachyspira species (range 16-64% similarity). This was further supported by average nucleotide identity values. Phylogenetic analysis performed using housekeeping genes and core genomes of all valid Brachyspira sp. and "B. hampsonii" revealed that B. suanatina and B. intermedia formed a clade distinct from B. hyodysenteriae. By comparing the genomes of the three closely related species B. intermedia, B. hyodysenteriae and B. suanatina similar profiles of general genomic features and distribution of genes in different functional categories were obtained. However, the genome size of B. hyodysenteriae was smallest among the species, suggesting the possibility of reductive evolution in the divergence of this species. A bacteriophage region and a putative plasmid sequence were also found in the genome of B. suanatina strain AN4859/03.
CONCLUSIONS
The results of our study suggest that despite being similar to B. hyodysenteriae phenotypically, B. suanatina should be regarded as a separate species based on its genetic characteristics. Based on characteristics presented in this report we propose that strains AN4859/03, AN1681:1/04, AN2384/04 and Dk12570-2 from pigs in Sweden and Denmark, and strains AN3949:2/02 and AN1418:2/01 isolated from mallards in Sweden, represent a unique species within genus Brachyspira. For this new species we propose the name B. suanatina for which the type strain is AN4859/03T (=ATCC® BAA-2592™=DSM 100974T).
背景
短螺旋体属目前包含七个有效种，它们寄生于哺乳动物和鸟类的肠道。在之前的一项研究中，一组从猪和野鸭中分离出的强溶血菌株被暂时描述为短螺旋体属内的一个新种，即“猪鸭短螺旋体”，并且在猪攻毒模型中证实了其具有肠道致病特性。
方法
在本研究中，基于细胞形态、生长特性、酶谱、DNA - DNA杂交（DDH）以及全基因组比较对猪鸭短螺旋体进行了特性鉴定。测定了猪鸭短螺旋体菌株AN4859/03的基因组草图序列，并与短螺旋体属所有有效种的现有基因组进行了比较。
结果
根据形态特征、生长特性和酶谱，猪鸭短螺旋体与猪痢疾短螺旋体的模式菌株相似，但使用DDH推荐的70%相似性阈值时，它不属于任何已确认的短螺旋体种（相似性范围为16 - 64%）。平均核苷酸同一性值进一步支持了这一结果。使用所有有效短螺旋体种和“汉普森短螺旋体”的管家基因和核心基因组进行的系统发育分析表明，猪鸭短螺旋体和中间短螺旋体形成了一个与猪痢疾短螺旋体不同的进化枝。通过比较中间短螺旋体、猪痢疾短螺旋体和猪鸭短螺旋体这三个密切相关种的基因组，获得了一般基因组特征和不同功能类别中基因分布的相似图谱。然而，猪痢疾短螺旋体的基因组大小在这些种中最小，这表明该种在分化过程中可能发生了简化进化。在猪鸭短螺旋体菌株AN4859/03的基因组中还发现了一个噬菌体区域和一个假定的质粒序列。
结论
我们的研究结果表明，尽管猪鸭短螺旋体在表型上与猪痢疾短螺旋体相似，但基于其遗传特征应将其视为一个独立的种。根据本报告中呈现的特征，我们提议来自瑞典和丹麦猪的菌株AN4859/03、AN1681:1/04、AN2384/04和Dk12570 - 2，以及从瑞典野鸭中分离出的菌株AN3949:2/02和AN1418:2/01，代表短螺旋体属内的一个独特种。对于这个新种，我们提议命名为猪鸭短螺旋体，其模式菌株为AN4859/03T（=ATCC® BAA - 2592™ = DSM 100974T）。
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